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(No Model.)

0. A. RANDALL.

Telephonic Transmitter.-

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llnirn warns a'rnsir TELEPHONIC TRANSMITTER.

SPECIFICATION forming part of Letters Patent No. 241,066, dated'May 3, 1881. Application filed February 8, 1881. (No model.)

To all whom it may concern:

Be it known that I, OnARLns A. RANDALL, a citizen of the United States, residing at New York, in the county of New York and State of New York, have invented new and useful Improvements in Telephonic 'Iransmitters, of which the following is a specification.

This invention relates to telephonic transmitters in which makes and breaks of an electric circuit result from the vibrations of the transmitting-diaphragm or other vibrator. It refers especially to an improvement upon the transmitting apparatus shown and described in Letters Patent No. 235,020, granted to me November 30, A. D. 1880.

In the transmission and reproduction of articulate speech by means of an intermittent current, or makeand-break electrical circuit, means for securing synchronous and uniform movements of the make-and-break contact.- points and the diaphragm or other vibrator are of vital importance, as extra vibrations of some or all of these points are liable to occur, thereby producing; in the receiver harsh and I have succeeded in overcoming these extrad'alse, and sympathetic vibrations.

In the accompanying drawings, Figure l is a side view, partially in section, of a telephonic transmitter constructed according to my invention. Fig. 2 is a plan view of one of the diaphragm-supporting rings detached. Fig. 3 is a similar view with the diaphragms arranged in their relative positions. Fig. 4 is a view, in detail, of the make-aud-break contact devices. Fi 5 is a view, partly in section, of a modified form of the transmitter. Fig. 6 is a detail View of a modification ot' the makeand-break contact devices. Fi 7 illustrates a make-and-break device for sending alternately-reversed currents over the line.

Referring to Fi 1, the letters A and A indicate two rings, which may be of any suitable rigid material, and each having its inner periphery formed on two half-circles of different diameters, as shown at a a in Fig.2. The rings in Fig. 1 are arranged with their said inner peripheries in coincidence. Between these two rings are clamped two semicircular metallic diaphragms, B and B, of cters and areas, as shown 1n Fig.

different diam- 3, and with their curved ed ges covered by rubber washers c 0, the smaller diaphragm B being clamped between the smaller portions of the peripheries of the rings, which are held together by screws (M, which serve, also, to secure the mouth-piece E to the t p ring. The straight edges of the diaphragms are slightly separated, and from the outer surface of the larger diaphragm:pro-

jects a bracket, F, having an arin,f, extending behind the smaller diaphragm, and provided with a metallic adjusting-screw, G, carrying on its tip a block, g, of carbon or platinum, directly opposite and impinging against a platinum plate, h, which is secured to the outer surface of the smaller diaphragm. The block and plate hare the contact-points 'by which the circuit is made and broken, and the linewire may be connected with the screw, and the smaller diaphragm connected with a battery, which is also connected with the ground. A yielding cushion may be interposed between theplatinum plate It and the smaller diaphragm, it found desirable.

Instead of being connected directly with the line, the contact-points may be in the primary circuit of an induction-coil, the secondary circuit of which is properly connected with the line and ground. The diaphragms may be of metal, wood, mica, or any other suitable material capable of responding to air-waves of articulate tones, proper connection being made between the platinum plate It and the battery. When arranged substantially as described the diaphragms, or virtually the contact-points, are actuated simultaneously and with the same power by air-vibrations, whether great or small, and are vibrated in unison, one vibrator or contact-point having, however, a greater amplitude of movement than the other, thus insuring a positive make and break of the circuit at each complete vibration of the diaphragms.

In the modification shown in Fig. 5 I provide the transmitter with two diaphragms, I and I, the upper and larger diaphragm, 1, being secured between the base of the mouthpiece E and a ring, 76, the said ring having apertures, through which the screws 1, projecting from the base a, fit loosely, the nuts m serving to hold said ring in position. A platinum stud, 0, projects downward from the center of the diaphragm I, and approaches very nearly to a carbon or platinum plate, 1), which is secured upon the center of the diaphragm 1, which has a less diameter than diaphragm I, and is clamped between the base a and a ring, 7a, which is held in position by screws Z.

The letter Q, indicates a piece of light rubber tubing, carried by an adjusting-screw, 1", tapped through a bracket, 8, secured to the base a. The said piece oftubing extends through an opening in the said base and impinges against the under side of the diaphragm I, serving the double purpose of a fine adjustment and damper for said diaphragm, the pressure of the piece of tubing against the diaphragm being regulated by the screw 1'. The proximity of the platinum stud 0 and the carbon or plati- 11 um plate 1) may also be regulated by the nuts m and m. The platinum stud is connected with the battery, and the carbon or platinum plate with the line, or vice versa. \Vhen airvibrat-ions strike the diaphragm I it will move in response thereto and cause the platinum stud 0 to make contact with the carbon or platinum plate 1), thus closing the circuit and eom municating movement to the smaller diaphragm but on the return movement, to complete the vibrations, the platinum plate cannot follow the stud through its whole movement, because of the greater amplitude of vibration in the diaphragm I, and thus a break of the circuit must occur, and always at the same point relative to the vibrations of the two diaphragms.

In Fig. 6 the larger diaphragm, B carries two brackets, F and F, projecting from its opposite surfaces, and provided with adjusting-screws G G, which are preferably tipped with platina. The brackets extend beyond the edge of the smaller diaphragm, B and the screw G may be adjusted to more positively control the movement of the contact-points, and to more positively insure contact than is the case in the modification shown in Fig. 4.

In Fig. 7 the larger diaphragm, B is provided with the two brackets F and F and adjusting-screws G and G while the smaller I diaphragm, B is provided with two contactplates, h h, of platinum or carbon, said contact-plates being connected with the opposite poles of a battery, w, the middle of which is connected to the ground. The larger diaphragm is connected to the line, and the screws may be so adjusted that when the diaphragms are vibrated said screws will alternately make contact with the opposite contact-plates, and thus the circuit be closed alternately from opposite ends of the battery, and reversed currents caused to traverse the line.

Instead of two sectional diaphragms having unequal areas, as shown in Figs. 1 and 3, or two circular diaphragms of different diameters, the diaphragms may have the same superficial area and onebe heavier than the other, so that when both are moved by the same force the lighter diaphragm will have a greater amplitude of movement, and thus act toward the heavier the same as does a larger toward a smaller diaphragm, as heretofore described.

What I claim is- 1. In a make-and-break telephonictransmitter, the combination, with adiapl'n'agm orother vibrator, of two or more vibratory contactpoints, arranged to move isochronously with diiterent amplitudes of vibration under the influence ot'said diaphragm or vibrator, and suitable means for adjusting and limiting the movement of said contact-points, substantially as described.

2. The combination, with the suitably-supported semicircular diaphragm B, carrying the bracket and adjustable contact-point, of the diaphragm B, of similar shape but less diameter and carrying the contact-plate, substantially as described.

3. In a make-and-break telephonic transmitter, the combination, with a diaphragm or other vibrator provided with two contact-points arranged for connection with a line-wire, of another diaphragm or vibrator arranged to move isochronously therewith with diflerent amplitudes of vibration, and carrying two contactpoints, respectively arranged for connection with opposite poles of a battery, and to make contact with said first-named contact-points alternately, substantially as described, whereby, when the diaphragms are actuated by airvibrations produced bysounds, currents of opposite polarity or direction will be caused to alternately traverse the line.

In testimony whereof I have hereunto set my hand in the presence of two subscribing witnesses.

CHARLES ADAMS RANDALL.

Witnesses:

FRANK R. LoRD, PHILIP G. RANDALL. 

